The six-string acoustic guitar has survived many centuries without much alteration to its original design. Prior to the present invention, one very important aspect of acoustic guitars that has been overlooked is proper intonation of each string—defined as adjusting the saddle longitudinally with the string until all of the notes on the instrument are relatively in tune with each other. Traditional methods of acoustic guitar construction intonate the high and low E strings which are connected to the bridge with a straight nonadjusting saddle. The other four strings are either close to being intonated or, as in most cases, quite a bit out of intonation.
Historically, discrepancies in intonation were simply accepted by the artist and the general public, as it was not believed that perfect or proper intonation on an acoustic guitar was attainable. The artist accepted this fact by playing out of tune in various positions on the guitar, or developed a compensating playing technique to bend the strings to pitch while playing, which was difficult and/or impossible to do.
Particularly in a studio setting, the acoustic guitar must play in tune with precisely intonated instruments and the professional guitarist cannot have a guitar that is even slightly off in intonation.
If, for example, the weather or temperature changes, the guitar string gauge is changed, string action (height) is raised or lowered, the guitar is refretted, or a number of any other conditions change, the guitar must be re-intonated. This especially plagues professional musicians who frequently travel or tour giving concerts around the country in different climatic zones. Such travel causes guitars to de-tune and spurs the need for adjustable intonation. Airplane travel, with the guitar being subjected to changes in altitude and pressures, exacerbates these problems. Accordingly, adjustability of intonation is desirable due to the many factors which seriously effect the acoustic guitar. Yet, most acoustic guitar companies still use the original nonadjustable single saddle.
In one aspect of the invention, the fully adjustable acoustic guitar bridge claimed herein is the only system known to the inventors that allows for continuous fully adjustable intonation of each string without sacrificing the sound of the instrument. Thus, there has been a need for the improved construction of adjustable intonation apparatus and methods to properly intonate acoustic guitars.
Attempts to properly intonate acoustic guitars have been made without success. In the 1960's, attempts were made by Gibson® with the Dove® acoustic guitar by putting a so called Nashville Tune-O-Matic bridge® on the acoustic guitar. The Tune-O-Matic was designed for electric guitars and although it theoretically allowed the acoustic guitar to be intonated, the electric guitar metal bridge destroyed the acoustic tone and qualities of the acoustic guitar. Accordingly, these guitars were believed to have been discontinued, or have not been accepted in the market, at least by professional guitar players. In the 1970's, a compensated acoustic guitar bridge was developed which cut the saddle into two or three sections and intonated the guitar strings individually with two, three, or four strings on each saddle. However, this method is not individually and continuously adjustable and thus has the major drawbacks listed above. It is important to note that traditional electric guitar bridges either have an adjustment screw running through the metal saddle, with the screw connected at both ends of the bridge (Gibson Tune-O-Matic), or springs loaded on the screw between the saddle and the bridge to help stabilize the saddle (as on a Stratocaster electric guitar). The above construction is not adaptable to acoustic guitars. On an acoustic guitar, if either the screw is connected at both ends of the bridge, or a spring is placed between the saddle and the screw, the saddle will be restricted in its vibration, thereby choking off or dampening the string vibration, resulting in lack of sustain (duration of the note's sound), or no tone or acoustic quality.
Additionally, typically, electric guitar bridges are not transferrable to acoustic guitars because electric guitar bridges are constructed of metal, which produces a bright tone with the electric guitar strings (wound steel as opposed to the acoustic guitar's wound phosphor bronze strings or nylon). The saddles on an electric guitar bridge are fixed (springs or the adjustment bolt connected at both ends of the bridge) since the pickups (guitar microphones) are located between the bridge and the neck and the electric guitar does not rely on an acoustic soundboard to project the sound. The electric guitar strings simply vibrate between two points and the vibrations are picked up by the electric guitar pickups.
The saddles for the acoustic guitar bridge typically cannot be made of metal (steel, brass, etc.). The acoustic guitar relies on the string vibrations to be transmitted from the saddles to the base of the bridge. The vibrations go from the bridge to the guitar top (soundboard) and on acoustic/electric guitars to the pickups; either internal under the bridge and/or connected against the soundboard to pickup the soundboard's vibrations. The saddle must be constructed of an acoustically resonant material (bone, phenolic, ivory, etc.) to transmit the string vibrations to the base of the bridge. Metal saddles would dampen these vibrations, and the acoustic guitar would produce a thin, brittle tone with very little or no sustain of the notes being played.
One aspect of the claimed invention solves these problems. The saddle capture has a slight bit of slop or looseness in its threading with the adjustment bolt. While round holes with clearance will work, the preferred hole is oval allowing maximum up and down freedom of movement. The saddle must have this small bit of freedom to vibrate in order to transmit string vibration into clear, full bodied tones that will ring and sustain through the projection of the acoustic guitars soundboard and/or internal pickup. In another embodiment (FIG. 6D), the set screw provides additional pressure on the saddle, eliminating any tendency of the saddle to “float” on the bridge base, providing even more sound transfer to the soundboard.
Another aspect of the present invention relates to making adjustments to the so-called Rule of 18. This aspect applies not only to acoustic guitars, but to electric guitars also. In fact, this aspect applies to any stringed instrument having frets and a nut, wherein placement of the nut has been determined by The Rule Of 18. The nut is defined as the point at which the string becomes unsupported in the direction of the bridge at the head stock end of the guitar.
After further research into the design flaw in the Rule of 18 as regards nut placement as set forth in U.S. Pat. No. 5,404,783 and in application Ser. No. 08/376,601, it became apparent that additional refinement resulted in even more accurate intonation. An additional refinement to the Rule of 3.3% compensation as set forth in the above patent and application (which is incorporated herein by reference) suggested that three separate Rules of Compensation, one for the electric guitar and two for acoustic guitars, were needed. For example, the Rule of 1.4% compensation applies to acoustic steel string guitars; for electric guitars, the Rule is 2.1% compensation. The Rule for nylon string acoustics is 3.3%.
The difference in compensation is due to decreased string tension on the electric guitars, relative to the higher tension on acoustic guitars. The decrease in overall string tension (open strings) results in more pitch distortion when playing fretted notes close to the nut (i.e. notes such as the F, F#, G, G#, etc.). The greater the pitch distortion at the 1st fret (assuming standard nut height of 0.010″˜0.020″), the more compensation in nut placement is required. Hence, we have what we call the Rule of 2.1% (or 0.030″ shorter than standard 1.4312″). The correct distance from the nut to the center of the first fret slot is 1.401″ on an electric guitar with standard 25½″ scale. Standard guitars are manufactured using a mathematical formula called the Rule of 18 which is used to determine the position of the frets and the nut.
A short explanation of the guitar is helpful to understanding this Rule of 18. The guitar includes six strings tuned to E, A, D, G, B, and E from the low to high strings. Metal strips running perpendicular to the strings, called frets 20, allow for other notes and chords to be played. (See FIGS. 1–4.) The positioning of the frets are determined by employing the Pythagorean Scale. The Pythagorean Scale is based upon the fourth, the fifth, and the octave interval ratios. As shown in FIG. 3, Pythagoras used a movable bridge 50 as a basis, to divide the string into two segments at these ratios. This is similar to the guitar player's finger pressing the guitar string down at selected fret locations between the bridge and the nut (FIG. 4).
To determine fret positions, guitar builders use a mathematical formula based from the work of Pythagoras called the Rule of 18 (the number used is actually 17.817). This is the distance from the nut (see FIG. 5) to the first fret. The remaining scale length is divided by 17.817 to determine the second fret location.
This procedure is repeated for all of the fret locations up the guitar neck. For example, focusing on FIGS. 5A and 5B, in an acoustic guitar with a scale length of 25.511″, the following calculations are appropriate:25.5□17.817=1.431″  (a) distance from nut to first fret25.5−1.431=24.069″24.069□17.817=1.351″  (b) distance between first and second fretor1.431+1.351=2.782″  distance from nut to second fretThe procedure and calculations continue until the required number of frets are located.
Some altering of numbers is required to have the twelfth fret location exactly at the center of the scale length and the seventh fret producing a two-thirds ratio for the fifth interval, etc.
Unfortunately, this system is inherently deficient in that it does not result in perfect intonation. As one author stated:                “Indeed, you can drive yourself batty trying to make the intonation perfect at every single fret. It'll simply never happen. Why? Remember what we said about the Rule of 18 and the fudging that goes on to make fret replacement come out right? That's why. Frets, by definition, are a bit of compromise, Roger Sadowsky observes. Even assuming you have your instrument professionally intonated and as perfect as it can be, your first three frets will always be a little sharp. The middle register—the 4th through the 10th frets-tends to be a little flat. The octave area tends to be accurate and the upper register tends to be either flat or sharp; your ear really can't tell the difference. That's normal for a perfectly intonated guitar.”(See The Whole Guitar Book, “The Big Setup,” Alan di Perna, p. 17, Musician 1990.        
While this prior art system is flawed, before this invention it was just an accepted fact that these were the best results that guitar makers could come up with. But even with the inventions set out in the inventor's prior patents (incorporated herein by reference), the system was not perfect. The inventor has discovered a method of intonating guitars and other stringed, fretted instruments that finally corrects additional discrepancies or deficiencies thought to be inherent in the design of the instrument.
This leads to another aspect of the invention. For centuries, the acoustic guitar has been intonated according to a standard formula, or method. That method consists of adjusting the saddle, (or saddles) so that each individual string plays “in tune” with itself at the 12th fret, meaning that an open string (for instance, “G”) in the 4th octave, should be “intonated,” or adjusted, so that the fretted “G” on the same string (12th fret, 5th octave) reads exactly one octave higher in pitch. This process is then repeated for all six strings, and once accomplished, results in a “perfectly” intonated guitar. The problem, however, is that this “perfectly” intonated guitar exhibits an annoying problem, one that has plagued guitarists since its invention. Certain chord shapes will sound beautiful and pleasing to the ear, while other chord shapes will sound “sour” or unpleasant to the ear. It has been a vexing and intractable problem, one that has defied all attempts to resolve it.
Efforts have been made to position the saddle more accurately, or to “compensate” the saddle (changing the witness point where the string actually leaves the saddle) so that the 12th fret note agrees more closely with the open string note, and, aided by the evolution of more precise machine tools, measuring devices, etc; we have, in fact, “perfected” this intonation method even more.
The basic problem, however, has remained and has resulted in enormous frustration for guitarists and luthiers, as well as guitar technicians, because, in spite of their best efforts to achieve “perfect” intonation, the guitar still sounds out of tune at certain chord shapes.
As indicated in the background of the invention, current intonation technology, even with the prior Feiten inventions set forth in U.S. Pat. Nos. 5,600,079 and 5,404,783, still has not resulted in pleasing intonation under the current framework using universally accepted models.
Indeed, prior artisans in the field may have even been saddled in trying to perfect a “bad”, imperfect or flawed model for at least 400 years. From a historical perspective, prior to the mid 1600's, pianos or claviers had evolved from a “just” or “mean” intonation (tuning the instrument to play in only one or two related keys) to “equal temperment”; i.e., tuning the instrument so that all the notes were mathematically equidistant from each other. This method was an attempt to allow the instrument to play in a variety of unrelated keys and still sound acceptably in tune. It was only partially successful and resulted in the entire keyboard sounding slightly out of tune, especially in the upper and lower registers.
In the mid-1600's, an enormous breakthrough occurred in piano technology. The “well tempered” keyboard was conceived, and with it, a new standard for piano keyboard intonation which we still use today.
With this perspective, the inventors believe that the reason that guitars still sound out of tune, in spite of “perfect” intonation, is that the universally accepted method for intonating guitars represents a form of “equal temperment” . . . a method that was abandoned in the 1600's by piano tuners! So, what the subject invention claims is a new intonation model; i.e., a “well tempered” model specific to the guitar. There are, in fact, four separate models, one each for nylon string, steel string acoustic, electric guitar, and bass guitar, as a function of string gauges.
The term “tempering” in the context of a guitar means deliberately adjusting the length of a string at the saddle point so that the 12th fret note is slightly “out of tune.” The inventor is claiming a method that results in “pleasing” intonation anywhere on the fingerboard, regardless of chord shape.
When a piano tuner intonates a piano, he uses one string as his “reference” note, typically, A-440 (or Middle “C”). He then “stretches” the intonation of the octaves, plus or minus a very small amount of pitch. These units of pitch are called “cents.”
He then “tempers” the notes within the octaves so that they sound “pleasant” regardless of the key. Best wisdom in the art dictated that “tempering” a guitar was impossible, due to the fact that on a piano, one string is always the same note, whereas on a guitar, one string must play a variety of notes, leading to the universal perception that such an attempt would present an insurmountable obstacle in terms of the complexity of mathematical pitch relationships.
The inventors discovered, however, that it is possible to apply a very specific and subtle formula that adjusts or “tempers” the intonation (both open string and 12th fret) to the instrument, so that the result, while mathematically “imperfect,” sounds “pleasant” to the listener, regardless of chord shape or position on the neck.
Attempts have been made to “compensate” the saddles on a guitar to “improve” the intonation, however, the attempts have been haphazard, random, arbitrary, and unsystematic, and have not resulted in a satisfactory solution.
The inventors have thus discovered a tempering formula utilizing specific pitch offsets, which when applied to the guitar, result in extraordinarily pleasing intonation.
The concept of using specific pitch offset formulae to “temper” a guitar is a completely novel concept.